1. Field of the Invention
The invention relates to a method for continuous measuring of dynamic fluid consumption, particularly of fuel, by means of a continuously-operating flow sensor with variable pressure drop, preferably a mass flow sensor, whereby the pressure beyond the flow sensor is adjusted to a constant value by means of a pressure regulator. The invention addresses furthermore a pressure regulator having a housing, which contains an element biased by a changeable force acting against the pressure to be regulated whereby Pie this element is coupled to a valve arrangement that is also arranged in the housing for the pressure build up of the fluid therein. The invention relates also to a device for continuous measuring of dynamic fluid consumption, particularly of fuel, comprising a tank, possibly a fuel conditioning system, and preferably a controllable pump, a continuously-operating flow sensor for the fluid, preferably a Coriolis sensor, and a initial-pressure regulator for the admission pressure between the flow sensor and the fluid consumer.
2. The Prior Art
Intermittently operating systems based on scales are known in the art for measuring consumption of fluids, especially in the application of fuel consumption of engines on test benches. They have the advantage of being open systems, namely they have the characteristic whereby fuel can be delivered from the measuring system and returned to the system at limited time-intervals and limited volume. The dispensed amount of fuel as well as the returned fuel amount are measured and taken into account in the consumption reading. Open systems are advantageous especially for modern injection systems since they force fuel back at the start of the engine during the pressure buildup, within limited volume, into the fuel supply system in case of motor vehicles this volume is drawn back to the vehicles tank. Such scales have been shown to be of disadvantage in that they have to be always refilled and a continuous measuring process is not possible thereby.
Measuring apparatuses are often used for continuous measuring which take volumetric measurements of the fuel flow. The used-up fuel mass is determined therein by means of an additional density measurement which represents the actually required quantity to be measured. Direct measurement of mass consumption, which avoids the disadvantage of an additional density measurement, can be presently realized only intermittently through the weighing method and continuously with Cajoles sensors.
Modern internal combustion engines require for proper operation defined and flow-dependent pressure conditions mostly in the fuel delivery line as well as in the possibly existing fuel return line.
According to the Austrian Utility Model No. 3,350, there is provided a pressure stabilization device for stabilization of the initial pressure of the mass flow sensor to be able to create the required low and constant pressure at the connection point to the consumer (generally a few milliards). In fact, the flow-dependent pressure drop at the mass flow sensor must be variably compensated (up to 2 bars, for example). In particular, highly frequent, erratic or pulse-like drawing of fluid must be quickly taken into consideration.
In the above-mentioned continuous method of fuel measuring, a pressure regulator is attached upstream from the actual flow sensor for pressure stabilization whereby the pressure regulator adjusts the flow-dependent pressure at the output of the measuring system to a constant exit pressure. The disadvantage of such a design is that conventional mechanical pressure regulators act like a “hydraulic diode,” which is to say that the flowing medium can flow through the regulator only in one direction, namely downstream. A measuring system designed with such a pressure regulator does not represent an open system. Should fuel have to be returned from the injection system into the measuring system—or should there occur thermal expansion of fuel through the increase in temperature by a consumer that has stopped running—then there develops often an inadmissibly high pressure increase in the fuel system, depending on the elasticity of the lines, which stresses the lines and the built-in devices and which must be compensated possibly by costly pressure compensating devices.
It was the object of the present invention to provide a method and a device that ensures continuous, accurate, timely and highly discriminating consumption measuring with regulated exit pressure for the fluid, and which permits a return flow of at least short duration and also temperature-related expansion of the fluid.